Manometer switch



9, 1939- P. 1.. LENZ MANOMETER SWITCH Filed Aug. 26, 1937 W ITN ESSESZ INVENTOR Pefer L Zenz ATTORNEY Patented May 9, 1939 PATENT O'FFlCE MANOMETER SWITCH Peter L. Lenz, Edgewood, Pa., assignor to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa.,

sylvania Application August 26,

2 Claims.

My invention relates to a manometer switch, and particularly to a manometer switch for controlling a vacuum pumping system.

In the operation of vacuum systems such as those employed in vapor electric converters it is customary to provide a high vacuum pump delivering gases into a suitable interstage reservoir, and periodically emptying the reservoir by means of a suitable roughing pump. To control the roughing pump it is customary to provide a manometer switch responsive to the vacuum in the interstage reservoir, this manometer switch making and breaking a motor current as indicated by the pressure in the interstage reservoir.

The manometer switches heretofore used have been unsatisfactory in that they were frequently damaged in handling or in transit because of splashing of the operating mercury into the interstage reservoir or its connecting pipes. Also -in the operation of such vacuum systems it is customary to use automatic vacuum valves to control the opening between the interstage reservoir'and the roughing pump. If, as sometimes happens, the interstage reservoir is suddenly filled to atmospheric pressure because of failure of the automatic valve or for any other reason, the manometer switch is frequently broken because of the sudden impact of the operating mercury against a fragile glass wall.

In the operation of manometer switches, difficulty has also been encountered because of the burning off of the metallic contact elements.

The manometer switch according to my invention eliminates these difficulties by providing a pressure inlet tube opening into the pressure element of the manometer in such a manner that splashing or disturbing of the mercury will not cause mercury to spill into the inlet pipes. This is accomplished by extending the inlet pipe and providing a reduced opening in spaced relation from the walls of the pressure chamber so that any agitation of the mercury will be in such a manner as to remove the mercury from the opening of the inlet pipe.

The switch chamber of the device is provided with a tapering dome-shaped top so that if the mercury is suddenly forced into the switch chamber it will be gradually reduced as to contact area instead of suddenly coming into contact with a relatively flat closure.

In order to prevent burning of the metallic contact elements, the switch chamber is provided with a suitable barrier which traps a quantity of mercury, suflicient to maintain the contact element constantly emersed. The actual making a corporation of Penn 1937, Serial No. 160,964

and breaking of the contact then takes place between mercury surfaces adjacent the bafile. Preferably the baffle is constructed by extending a connecting passage from the pressure chamber into the switch chamber and extending it a sufficient length to provide the desired mercury trap.

It is the object of my invention to provide a pressure-responsive switching device which will not be damaged in shipping or other handling.

It is a further object of my invention to provide a manometer switch having a shape adapted to absorb a'mechanical pressure due to surging of the operating mercury.

It is a further object of my invention to provide a manometer switch in which the makingand breaking of the contacts is made between mercury surfaces.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing in which:

Figure 1 is a sectional elevation of the manometer switch embodying my invention, and

Fig. 2 is a pressure system showing the manner of utilizing my invention.

The illustrative embodiment, according to my invention, comprises a manometer I having a pressure chamber 2 connected to a pressure tube 3 and a switch chamber 4 containing the elements for making or breaking the contact. The inlet tube 3 to the pressure chamber 2 extends inwards, preferably through the top portion thereof, and has a tapered cone tip portion 5 having an opening 6 spaced from the walls of the pressure chamber 2, so that any liquid splashed against the walls will not enter the pressure tube 3. Preferably the inlet opening 6 of this tube 3 is of relatively small diameter.

The pressure chamber 2 and the switching chamber 4 are connected by a suitable passage 1, preferably of U-shape. The passage 1 extends from the bottom of the pressure chamber 2 to the bottom of the switching chamber 4, preferably the passage extends upward into the switch chamber 4 to provide a suitable bafile 8 which traps a quantity of mercury 9 constantly in the bottom of the switching chamber 4. A quantity of mercury l0 substantially fills the U-shaped passage 1 and the bottom portion of the pressure chamber 2.

The variations in pressure in the pressure chamber 2 cause the operating mercury ID to rise and fall in the switch chamber 4 to make or break contact with the trapped mercury 9.

A metallic element II is sealed in permanent contact with the trapped mercury 9 while another metallic contact I2 is connected into the passage tube I so as to make contact with the mercury III in the passage I. The switch chamber 4 is provided with a tapering dome-shaped top I5, preferably of increased thickness so that in the event air or in general, pressure is suddenly admitted to the pressure chamber 2, the surge of mercury I into the switch chamber 4 will be applied to a constantly reduced area so that the shock will be gradually. absorbed without injury to the manometer.

In the application of my invention as shown in Fig. 2, a manometer I is connected to a suitable pressure chamber herein illustrated as an interstage reservoir 20, the entrance 2| of which is connected through a suitable high vacuum pump (not shown) to any chamber which it is desired to evacuate. The entrance from the high vacuum pump being through a suitable barometrical seal 22, the outlet from the interstage reservoir is made through a suitable automatic vacuum valve 23 to a roughing pump, preferably, a rotary oil pump 24. The motor 25 for driving the rotary pump 24 is controlled by means of the contact elements II and I2 of the manometer switch I. When the rotary pump 24 has evacuated the interstage reservoir 20 to a certain suitable degree the pressure in the pressure chamber 2 in the manometer I will be reduced to permit the mercury I0 in the switch chamber to separate on the edge of the trapping bafile 8, which interrupts the current to the motor. If it is undesirable to have the mercury switch I interrupt the motor current, a suitable relay 26 may be interposed so that only the relay current need be interrupted by the switching device I.

If, as sometimes happens the automatic valve 23 should get stuck or otherwise fail to operate at a time that the pump 24 is inoperative, the oil in the pump would flow through the vacuum valve 23 into the interstage reservoir 20. For this reason, a suitable oil trap 21 has been provided in the interstage reservoir 20. The sudden increase in pressure in the interstage reservoir 20 would violently force the operating mercury II] into the switch chamber 4. However,

because of the tapered dome-like shape of the top I of the switch chamber 4, the pressure of the surging mercury It] would be gradually applied to the top I5 of the chamber 4 so that no damage would result.

Although I have shown and described a specific embodiment of my invention, it will be apparent to those skilled in the art that many changes and modifications can be made therein without departing from the true spirit of my invention or the scope of the appended claims.

I claim as my invention:

1. A mercury contact device responsive to pressure variation comprising a pair of chambers, a U-shaped passage connecting said chambers, a quantity of mercury in each of said chambers and substantially filling said passage, one of said chambers having a conduit connected to the source of control pressure, said conduit having a tapered end portion extending into and opening adjacent the central portion of the chamber for preventing spilling of mercury into said conduit, said U-shaped passage extending into said second chamber and providing an upstanding partition for trapping a quantity of mercury in said second chamber, an electrical connection to said pool of trapped mercury, an electrical connection to the mercury in said U-shaped passage, said second chamber having a tapered dome-shaped top.

2. A manometer switch including a pressure chamber, a tube connecting said pressure cham her to a source of pressure, said tube extending into said pressure chamber and having a restricted opening spaced from the walls of said chamber, a switch chamber, a passage interconnecting said chambers, a quantity of mercury in said pressure chamber and substantially filling said passage, a contact element in said switch chamber, a second contact element connected to said mercury, said mercury varying in level in said passage in response to the pressure in said pressure chamber to make or break contact with said contact elements, said switch chamber having a tapered top portion to prevent breakage by mercury on sudden changes of pressure.

PETER L. LENZ. 

